This invention concerns a new and improved one-piece, integral card guide unit for use in guiding and supporting circuit boards in a circuit board card cage. Circuit board card cages are well known. The general structure of such a card cage is shown and described and the publication VME Bus Specification Manual, Rev. c.1, October 1995, pages 215-247 of this publication by Motorola entitled xe2x80x9cSeries in Solid-State Electronics Rev. c.1; which publication is also entitled xe2x80x9cThe VME Bus Specificationxe2x80x9d dated October 1995. This VME Bus Specification Manual also is known as the xe2x80x9cIEC 821 Busxe2x80x9d and the xe2x80x9cIEEE P1014/d1.2,xe2x80x9d and was printed by Printex Publishing, Inc.
Such circuit board card cages generally comprise enclosures having side walls and a back plane, secured together in a frame that comprises elongated front and rear cross members connected to the upper surface of the side walls and back plane and to the lower surface of the side walls and back plane, to form the circuit card rack enclosure. This enclosure is often open in the front, top and the bottom to allow air circulation around the individual circuit boards to cool the electronic components. The top and bottom and front openings can be closed if desired.
Positioned within the card cage structure are card rails or guides that extend generally between the front and rear cross members. These card guides have grooves that are opposing between the lower and upper card guide rails, for receiving the edges of the circuit boards. The card guides are also laterally spaced from each other, to provide space between the electrical and electronic components secured to the circuit boards. At the end of the known circuit boards, there is an electrical connection that interconnects with an electrical connection on the rear panel, known as the back plane electrical connector. The card rails in these card cages are often individually located and secured to the front and rear cross members in a manner to provide a vertical orientation of the circuit board to align the electrical connection on the circuit board with the electrical receptacle on the back plane. Here, problems arise in that the card rails often become skewed, moved or twisted by vibration or in the general use of the card cage, which can include shocks received by the card cage or just the overall use of the card cage in the environment in which the card cage is located. Such occurrences cause the circuit board to become misaligned to the extent that a good easy straight forward and precise connection cannot be made to the electrical circuit on the back plane. Further, in many card cages, the structure of the card rails and indeed the card cage in general is made of light sheet metal type construction or of plastic or other suitable materials. In these assemblies, there is a weak or insufficient connection between the card rails and the cross support members that will prevent slight movements or skewing of some of the card rails relative to other card rails which skews the position of the circuit boards. There are also some card guides units that are connected to the cross members in a manner where it is possible for the card guides to move relative to the cross member. This skews the circuit board in the guide relative to the opposing card guide, which again has an adverse effect on the circuit board being able to make the correct electrical connection.
So, there is a definite need for a new and improved circuit board card guide rail in which the card guide bars are integral with the multiple cross members, so that identical card rack guide units are connectable to the side walls and back plane of the card cage. This provides precise alignment of the circuit board with the back plane electrical connections, is not subject to twisting and other movements between the card guides and the cross members, and which card guides are formed in a manner that allows some transitory tolerance to twisting, vibration and other shocks to the card cage, while still maintaining permanent, precise alignment of the circuit board with the back plane electrical connections.
This invention concerns a new and improved one-piece, integral circuit card guide unit. This new circuit card guide unit is preferably made of metal. All parts, including the front and rear cross members and the elongated card guides, are all made in one integral unit. The new and improved construction of this guide unit provides a strong integral structure that when mated with an identical guide unit, in opposed relationship, and secured between two side walls at the outer ends of the respective cross members, provides a card rack in which the circuit boards or cards are directly aligned with the back plane electrical connection, and the integral construction holds this precision alignment through use of the card cage in many environments. This integral structure, which is preferably made of aluminum, is extruded to provide the cross members. An interconnecting portion of the aluminum plate is then machined to provide the precision elongated card guides with a U-shaped recess, that is rigidly and integrally secured in position relative to the rest of the rack unit. In the shaping of the elongated card guides, the metal content therein is reduced to that required to maintain the rigidity and functionality of the card guides, while still allowing slight flexing as may be advantageous in aligning the circuit boards with the electrical contacts on the back plane. Further, elongated, longitudinal, U-shaped card guides of protective insulated material can e snapped into or fitted into the U-shaped recesses in the cad guide for receiving, guiding and positioning the respective outer edges of the circuit boards.
This invention eliminates the problems of prior devices by the integral connection between the ends of the card guides and the cross members. The problems with these connections become major in prior art devices, because regardless of the connection that is made, this connection still allows movement of the card guides relative to the cross members and thus relative to the electrical connections on the back plane. Also, since this invention is not just an extruded product, it can be machined to required tolerances to achieve the desired rigidity and strength, with the desired reduction of weight and non-flexibility. Further, since each of the rack units are identical, the problems encountered in having different sizes, or different shapes, or different length ends of the cross members, all of which affects the alignment of the opposing card guides when installed in a card cage, are eliminated.
It is therefore an object of this invention to provide a new and improved card guide unit.
It is another object of this invention to provide a new and improved integral card cage rack unit that is machined to close tolerances for lasting, precision alignment of circuit boards with the back plane electrical connections.
It is another object of this invention to provide a new and improved integral card cage rack unit, that in combination with known circuit board card cages having two side walls and a back plane, provide a new and improved overall card cage.